A control unit of which case is constituted by a base, a cover and a connector member, and of which circuit board is disposed inside the case, has been known. On each periphery of the base, the cover and the connection member, a joining surface on which a convex line or a concave line is formed, is disposed. On each boundary of the base, the cover and the connector member, a seal portion is formed where the convex line and the concave line facing each other are coated with a seal material and engaged with each other, in order to improve waterproof performance (see PTL 1).